It started around February, when Republicans were still eager to talk about contraception. The Obama administration, or so Mitt Romney charged in Colorado, was forcing religious institutions to provide “morning-after pills –in other words abortive pills — and the like, at no cost.”

It was, of course, a lie. Romney was conflating two different pills: emergency contraception, known as the morning-after pill, which prevents a pregnancy; and chemical abortion, or mifepristone, which ends a pregnancy of up to seven weeks’ gestation and isn’t covered under the new guidelines. Since both pills were marketed in the U.S. around the same time, even some pro-choicers have gotten confused. But Colorado happens to be the epicenter of people confusing them on purpose. It’s the birthplace of the Personhood movement and home to Focus on the Family, both of which have strategically called emergency contraception “abortion” on the scientifically unproven basis that they could block a fertilized egg from implanting.

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Part of the reason people get confused about emergency contraception and abortion is because lots of people are confused about the basic biology of pregnancy: specifically, that it doesn’t necessarily happen instantaneously and that sperm can live in the body for several days, during which time a woman can ovulate and an egg can potentially be fertilized and implant. Regular use of hormonal contraception prevents ovulation and the chance for fertilization; emergency contraception essentially works the same way except that it’s taken after sex, by which point ovulation may have already happened. But according to recent studies, there is no evidence that taking emergency contraception after ovulation and fertilization will stop the egg from implanting.